The present invention relates to an image recording apparatus for recording an image of an original on a recording medium.
Various types of picture image recording apparatus have been developed in the art. One such picture image recording apparatus is disclosed in Japanese patent application No. 61-277595 filed Nov. 20, 1986 (corresponding to U.S. patent application No. 50,313).
In the disclosed apparatus, a print head is actuated in response to a signal indicative of image information to be recorded to impact upon an ink ribbon coated with a layer of non-light-transmissive ink for forming a light-shielding intermediate picture image on an intermediate sheet in the form of a light-transmissive sheet. Light is applied to the side of the intermediate sheet on which the light-shielding image is present, and passed through the intermediate sheet to expose a photo-sensitive pressure-sensitive recording sheet used as a photosensitive recording medium, to the image. The time required to form the intermediate image on the intermediate sheet in the above apparatus is shorter than the time required by earlier picture image recording apparatus to form light-shielding images of respective colors on an intermediate sheet through an electrophotographic process or a thermal transfer process. The apparatus disclosed in the above application is also small in size and requires easy maintenance only.
When exposing the photosensitive pressure-sensitive recording sheet to the image, it is necessary to hold the photosensitive pressure-sensitive recording sheet and the intermediate sheet at rest in superposed relation in order to prevent the image formed on the photosensitive pressure-sensitive recording sheet from being shifted out of registry. To meet this requirement, the formation of the light-shielding image on the intermediate sheet has to be interrupted temporarily. Therefore, light-shielding images cannot be successively formed on the intermediate sheet, and the period of time until a final picture image is recorded cannot be reduced.
The aforesaid problem manifests itself when respective light-shielding images of colors that make up a color picture image are formed on an intermediate sheet. The rate of speed at which such a color picture image is formed is thus low.
FIG. 1 of the accompanying drawings illustrates another conventional color picture image recording apparatus. The illustrated apparatus includes a laser printer 70 serving as an intermediate image generator for forming intermediate images of three separated colors such as cyan, magenta, and yellow on intermediate sheets 62 serving as light-transmissive mediums. The intermediate images of separated colors are then formed on photomask plates 81 (hereinafter referred to as "mask members") based on the color picture image information. The mask members 81 are then brought into intimate contact with a photosensitive pressure-sensitive recording sheet 92 as a color photosensitive pressure-sensitive recording medium. Then, a red-light lamp 93a is energized for the cyan mask member, a green-light lamp 93b is energized for the magenta mask member, and a blue-light lamp 93c is energized for the yellow mask member, to expose the photosensitive pressure-sensitive recording sheet 92, thereby forming a latent image thereon. The photosensitive pressure-sensitive recording sheet 92 is of the image transfer type. After exposure, the photosensitive pressure-sensitive recording sheet 92 is superposed on a color developer sheet 112 supplied from a color developer sheet cassette 111. The superposed sheets 92, 112 are then fed between two pressure developing rollers 121 to develop the latent image into a color picture image on the color developer sheet 112, which is thereafter discharged onto a tray 131.
The time required to expose the photosensitive pressure-sensitive recording sheet 92 in intimate contact with the mask members 81 is longer than the time required to form one mask member with the laser printer 70. Therefore, the laser printer 70 must refrain from forming a next mask member until the exposure of the photosensitive pressure-sensitive recording sheet 92 to the mask members 81 is finished. Stated otherwise, the formation of a light-shielding image on an intermediate sheet has to be interrupted temporarily. Therefore, light-shielding images cannot successively be formed on the intermediate sheet, and the period of time until a final picture image is recorded cannot be reduced.
Image information may be recorded on a photo-sensitive pressure-sensitive recording sheet in different ways. For example, image information may be scanned and exposed directly to a photosensitive pressure-sensitive recording sheet by using switchable light such as a laser beam. Alternatively, light information may be written on a photosensitive pressure-sensitive recording sheet with a microshutter such as by disposing a liquid crystal light shutter between the sheet and a continuously energized lamp. These methods however have the following problems:
With respect to the former method, photosensitive pressure-sensitive recording sheets that are presently manufactured have spectral sensitivities below a wavelength .lambda.=475 nm. Therefore, the laser beam source for scanning and exposing the sheets should be an argon laser beam source (wavelength .lambda.=351 nm), a krypton laser beam source (wavelength .lambda.=351 nm), a helium-cadmium laser beam source (wavelength .lambda.=325 nm), or an ultraviolet gas laser. These laser devices are however large in size and expensive.
As regards the latter method, where a liquid crystal light shutter is employed as the microshutter, the liquid crystal itself is deteriorated by ultraviolet radiation.
A picture image recording apparatus designed to eliminate the aforesaid difficulties is disclosed in Japanese Kokai Publication No. 62-231965 (corresponding to U.S. patent application No. 32865).
In the disclosed picture image recording apparatus, a latent image corresponding to a picture image on an original is formed on a transparent photosensitive body as a latent image carrier and a light-shielding material is coated on the latent image. A photosensitive pressure-sensitive sheet and an exposure device are disposed one on each side of the transparent photosensitive body, and the sheet is exposed to light from the exposure device through the light-shielding material and the transparent photosensitive body.
The sheet carries a multiplicity of microcapsules on its surface. The microcapsules can be hardened by exposure to light, but remain soft unless exposed to light. The microcapsules as hardened by exposure to light are not ruptured when pressure is applied to the sheet. Those microcapsules which are soft because light is prevented from being applied thereto by the light-shielding material are however ruptured by such pressure. The recording sheet therefore develops color by a coloring agent contained in the microcapsules. Therefore, a picture image corresponding to the latent image on the transparent photosensitive body is formed on the sheet. The developed picture image is identical to the picture image on the original. Thus, the picture image on the original is duplicated.
The picture image recording apparatus described above is free from the problems of the conventional apparatus using a photosensitive pressure-sensitive sheet, i.e., large size of the exposure scanning means and deterioration of the microshutter.
However, the above picture image recording apparatus is still disadvantageous in that since a drum-shaped photosensitive body and toner are employed, the apparatus is complex in structure, large in size, expensive to manufacture, and requires a high running cost due to maintenance of the photosensitive body and other components.
Further, U.S. Pat. No. 4,399,209 discloses a transfer type recording medium in which a developer material is coated on a separate substrate as a separate developer or copy sheet. Furthermore, U.S. Pat. No. 4,440,846 discloses a self-contained type recording medium in which an encapsulated chromogenic material or dye precursor and a developer material are codeposited on one surface of a single substrate as one layer or as two contiguous layers.